In many areas of the country and the world, the tap water has a very high sodium, chloride and bicarbonate content, and in general is too alkaline for containerized plants. Containerized plants are especially susceptible to high-alkaline problems since the roots are confined in an enclosed area in which alkaline water has time to penetrate and be absorbed by the soil in the enclosed area, and no "flushing" of the salts out of the soil usually takes place. When containerized plants are subjected to too alkaline a growing medium, the growth of the plants is retarded, and the plants may wither and die. Also, when the pH is too high, the availability of some nutrients to the plants is diminished with further adverse effects on the plants. The addition of more tap water to the plants aggravates the situation even more since it is the tap water that builds up the alkalinity of the soil.
The problems caused by the application of tap water with high alkalinity to containerized plants is compounded by the fact that many nurserymen use a large amount of peat moss when potting plants, and the peat moss has a large affinity for -- that is, a high exchange capacity with -- salts (i.e., carbonates, bicarbonates, sodium and chlorine). Therefore, the salt content built up in the soil for the containerized plants is even more hazardous than if some other type of soil and the normal tap water were used. Also, oftentimes fertilizers that are applied to the plants can aggravate the problems associated with high alkalinity.